1. Field of the Invention
This invention relates generally to a method and apparatus for shrinking skin tissue without damaging the melanocytes and other epithelial cells, and more particularly to a method and apparatus that creates a reverse thermal gradient in order to achieve skin tightening through partial denaturation of collagen without ablation of the collagen and without affecting the melanocytes and other epithelial cells.
2. Description of Related Art
The skin is the one organ of the body that is readily available for inspection by the eyes and fingers of every living person. It is subjected to considerable abuse such as exposure to extreme environments of cold, heat, wind, and sun.
The surface layer of the skin is called the epidermis. It is the barrier that prevents most substances from entering the body from outside while preventing body fluids from entering equilibrium with the environment. The basilar layer of the epidermis includes the melanocytes and other epithelial cells.
The melanocytes are small cells with a small, dark staining nucleus and a clear cytoplasm. Melanin in packaged in distinctive granules is produced by these cells and transferred then air dendritic processes to adjacent keratinocytes. The purpose of melanin is to protect the skin from the ravages of ultraviolet radiation. Beneath the epidermis is the papillary dermis and reticular dermis. Collagen tissue is found in the dermal and the sub dermal tissues.
There has been a large market for tightening the skin in order to reduce aging effects and effects created by exposing the skin to extreme environmental forces. To date there are two primary methods for tightening skin. The first is surgical skin excision. The second is chemical burn. When skin is surgically excised it leaves large scars. This is generally not a satisfactory solution for many skin tightening applications. With chemical peel treatments the process is painful, there is damage to the melanocytes and other epithelial cells, the patient maybe have spotted pigmentation, or with most of the melanocytes and other epithelial cells destroyed the patient can have a predominately white complexion. In the chemical peel method a thermal gradient is created which is hotter at the surface of the epidermis and cooler at the sub dermal layers. With the creation of this type of thermal gradient there is a great likelihood of modification or destruction of the melanocytes and other epithelial cells, resulting in blotchiness or an inability to tan in the future.
Collagen molecules are produced by fibroblasts which synthesize three polypeptide chains that wrap around one another in a triple helix. Each of the chains is approximately 1000 amino acid units in length, with glycine recurring regularly every third unit and hydroxyproline and proline recurring very frequently. Cross-linking occurs between the side, not the ends, of collagen molecules and is coupled with the amino acid composition to give collagen its great strength. Collagen tissue shrinkage takes place in a direction parallel to an axis of collagen fibers.
The phenomenon of thermal shrinkage of collagen begins with a denaturization of the triple helix of the collagen molecule. Partial denaturization of collagen tissue results in a shrinkage of the collage and provides a xe2x80x9ctighteningxe2x80x9d effect on the overlaying skin. To date there have been no devices or methods for contracting the underlying collagen tissue through partial denaturization without damaging the melanocytes and other epithelial cells in the epidermis.
Adipose tissue, more commonly known as fat, is formed of cells containing stored lipid. Adipose tissue is often subdivided into small lobules by connective collagen tissue serving as the fibrous septae.
Adipose tissue is widely distributed in the subcutaneous tissue but exhibits regional differences in amount partially because of age and sex. Excess adipose tissue can be physically undesirable from both health and cosmetic perspectives. A current method for the removal of fatty tissue is the extraction of adipose tissue by liposuction. This is a purely mechanical method with undesirable side effects due to the invasive nature of the process.
Another method of removing fatty tissue is disclosed in U.S. Pat. No. 5,143,063 (xe2x80x9cthe ""063 patentxe2x80x9d). The method of the ""063 patent targets adipose tissue which absorbs sufficient energy resulting in cell destruction and death. The method of the ""063 patent fails to minimize damage to the melanocyte in the epidermis. Thus, the method of the ""063 patent can create unwanted blotchiness or changes in the melanocytes and other epithelial cells.
There exists the need for skin tightening without damaging the melanocytes and other epithelial cells, or without surgical intervention. There is a further need for non-surgically removing adipose tissue without damaging the melanocytes and other epithelial cells.
It is an object of the present invention to provide a method and apparatus for tightening skin without substantially damaging the melanocytes and other epithelial cells.
Another object of the present invention is to provide a method and apparatus for tightening skin with the use of a thermal energy source that does not substantially effect the melanocytes and other epithelial cells.
Yet another object of the invention is to provide an inverse thermal gradient from the epidermis to the underlying collagen tissue.
A further object of the invention is to provide a method and apparatus for creating a reverse thermal gradient from the epidermis through a subcutaneous layer of soft tissue.
Still a further object of the present invention is to provide a method and apparatus for tightening skin through the use of an RF energy source and an electrolytic solution which transfer RF energy from RF electrodes to the epidermis and underlying layers.
Yet another object of the present invention is to provide a method and apparatus for creating a reverse thermal gradient that utilizes one or more RF electrodes, an electrolytic solution to transfer RF energy from the RF electrodes to the epidermis and underlying layers, and wherein the apparatus includes a lumen adapted to receive a cooling fluid.
These and other objects of the invention are provided in an apparatus for applying radiant energy through the skin to underlying collagen tissue without substantially modifying melanocytes and other epithelial cells in the epidermis. The apparatus includes a porus membrane adapted to receive an electrolytic solution and become inflated to substantially conform a contacting exterior surface of the membrane to a skin layer. The membrane includes a cooling lumen for receiving a cooling fluid. One or more thermal electrodes are positioned in the membrane and transfer thermal energy to the electrolytic solution. The electrolytic solution and cooling fluid create a reverse thermal gradient from the skins surface to the underlying collagen tissue. A thermal power source is coupled to the thermal electrodes, and a source of electrolytic solution is coupled to the membrane.
A method for tightening skin comprises providing a membrane in a thermal energy source. A reverse thermal gradient is created which cools the surface of the skin while heating underlying collagen containing layers. The skin and underlying collagen containing tissue are then heated without substantially modifying the melanocytes and other epithelial cells in the epidermis. The result is a contraction of collagen tissue and a tightening of the skin.
Radiant energy is applied to a variety of different skin layers including the papillary dermis layer, the reticular dermis layer, and even to a subcutaneous layer and to underlying soft tissue. One suitable energy source is one or more RF electrodes. Electrolytic solution transfers RF energy from the RF electrodes to the underlying collagen tissue. The cooling fluid can create a reverse thermal gradient at the epidermis to underlying desired layers of about 30 degrees to about 80 degrees C. The apparatus can further include one or more thermal sensors positioned on the contacting exterior surface of the membrane, as well as one or more impedance monitors. Further, the apparatus can include a feedback device which is responsive to a detected characteristic of the skin or subcutaneous layer in order to provide a control delivery of RF energy from the RF electrodes. A variety of detected characteristics can be monitored including impedance measurements of the skin and temperature profiles of the skin.
The feedback device can also include a controller as well as a multiplexer.
The creation of the reverse thermal gradient provides for the controlled contraction of collagen tissue, e.g., partial denaturization of the collagen molecules that results in a shrinkage of the collagen tissue, which then extends to a shrinkage of the skin. Creation of the reverse thermal gradient is different from other methods of collagen contraction which typically employ a thermal gradient that has a higher temperature at the surface and decreases with the depth of penetration.
The apparatus of the present invention that creates the desired contour effect by the modification of collagen tissue surrounding loculations of fat can include a focussing element to help direct the energy past the epidermis and into the fat containing layers. The apparatus can further include a coupling device that couples the focussing element to the membrane, as well as a bracket which is positioned around the periphery of the membrane and also supports the focussing elements. Instead of killing cells, thermal lipolysis is utilized with a cooling blanket on the skin so that thermal destruction fat cells, and the melanocytes and other epithelial cells are minimally damaged.
A variety of thermal energy sources can be employed. Suitable energy sources include but are not limited to RF, microwave, ultrasound and the like. In one embodiment, the preferred energy source is RF.